Selectively porous bodies and method for the preparation thereof

ABSTRACT

Flexible open celled foam is impregnated with a hardening resin and a portion of the foam collapsed to form a solid portion and the hardening resin cured to produce selectively porous bodies.

w. T.'MMICHAEL 3 572 390 March 1971 SELEGTIVELY POROUS BODIES AND METHODFOR THE PREPARATION manner" Original Filed Nov. 21, 1966 'IIIIII'II.INVENTOR. Wa//ace 7. M MIChae/ XMZZQ M AGENT United States Patent()flice 3,572,390 SELECTIVELY POROUS BODIES AND METHOD FOR THEPREPARATION THEREOF Wallace T. McMichael, Lake Jackson, Tex., assignorto The Dow Chemical Company, Midland, Mich.

Original application Nov. 21, 1966, Ser. No. 595,934, now

Patent No. 3,519,708, dated July 7, 1970. Divided and this applicationMar. 26, 1969, Ser. No. 840,565

Int. Cl. F1511 1/02 U.S. Cl. 138-41 6 Claims ABSTRACT OF THE DISCLOSUREFlexible open celled foam is impregnated with a hardening resin and aportion of the foam collapsed to form a solid portion and the hardeningresin cured to produce selectively porous bodies.

This application is a divisional application of my cpending applicationSer. No. 595,934, filed Nov. 21, 1966, and issued as U.S. Pat. No.3,519,708.

This invention relates to selectivel porous bodies and to a method forthe preparation thereof and more particularly relates to selectivelyporous bodies of synthetic resins Open celled foam.

Oftentimes, it is desirable to provide bodies having selective porosity,that is, bodies which are porous only in desired areas. Such bodiesoftentimes are useful as filters, distributors, dispensing heads,dispensing conduit and the like. Usually in the preparation ofselectively porous bodies such as filters, dispensing conduits and thelike, it is necessary to prepare a porous body and clamp or fasten theporous body to a support in such a manner that it is retained in thedesired position. Frequently, the techniques required for fabricatingsuch articles are expensive and time consuming, require a diversevariety of materials. For example, an organic filter element such asopen celled foam fibrous mat or the like, a support means to preventundesired deformation of the element and a means to secure the porouselement to a body are required to provide a selectively porousstructure. By the term porous body is meant a body which is permeable toa gas or liquid and permits the flow of a gas or liquid therethrough.The term porous as used herein does not contemplate a plurality ofclosed non-interconnecting cells which are impermeable to fluid flow.

It would be advantageous if there were available an improved permeableselectively porous body having a generally homogeneous composition.

It would also be advantageous if there were available an improved methodfor the preparation of synthetic resinous porous bodies.

It would also be advantageous if there were available an improved methodof preparation of synthetic resinous selectively porous bodies whichwould permit a wide latitude of operation in the preparation thereof.

It would also be beneficial if there were available improved selectivelyporous bodies of a synthetic resinous composition which were resistantto chemical attack.

These benefits and other advantages in accordance with the presentinvention are achieved in a method for the 3,572,390 Patented Mar. 23,1971 preparation of a selectively porous body. The steps of the methodcomprising: impregnating an open celled flexible foam with a settableresin and curing agent therefor, expressing excess resin from the foamand leaving a small quantity of resin coating in the open cells, thequantity of resin being insuificient to fill the cells, forming theresin coated flexible foam into a desired shape, allowing a selectedportion of the open cell foam to retain the open cells and collapsing aselected portion of the foam to form a substantially continuousnon-porous portion and effecting the cure of the settable resin.

Also contemplated within the scope of the present invention is animproved selectively porous body comprising a porous portion of alightweight flexible foam having open cells coated with a thin film of ahardened resin and a curing agent therefor, and an impervious portioncomprising a collapsed portion of the foam wherein the cell walls areadhered together by the hardened resin.

Settable flexible foamed resins are disclosed in U.S. Letters Patent3,269,887 wherein a flexible foam is impregnated with a settable resin.An impregnated flexible foam containing sufficient resin to wet thesurfaces of the open cells is deformed to provide a desiredconfiguration and the resin is caused to cure or set imparting apermanent configuration to the resultant structure Suitable flexibleopen celled foams, hardenable resins and the like are disclosed in U.S.Pat. 3,269,887, employing the hereinbefore described settable foams. Avariety of highly useful products are readily fabricated.

The benefits and advantages of the present invention will become moreapparent from the following specification taken from the drawingwherein:.

FIG. 1 is a sectional view of an article in accordance with the presentinvention.

FIG. 2 is a view of a distribution conduit prepared in accordance withthe present invention.

FIGS. 3 and 4 depict one method of the formation of articles accordingto the invention.

FIGS. 5 and 6 depict an alternate method of preparing the articles inthe present invention.

FIG. 7 is a schematic representation of an air-duct employing aselectively porous article in accordance with the present invention.

In FIG. 1 there is illustrated a pipe line filter in accordance with thepresent invention generally designated by the reference numeral 10. Thefilter 10 comprises a body or housing 11. The housing 11 has a first end12 and a second end 13. The body 11 defines therein an internalpassageway 14 extending from the first end 12 to the second end 13. Thepassageway 14 defines an enlarged portion 14a lying between the firstend 12 and the second end 13. Flanges 16 and 17 are formed by the body11 at the first end 12 and second end 13, respectively, to facilitatecoupling or connection to a piping system. Disposed within the enlargedportion 14a or of passage cavity 14 is a hardened or rigid flexible foamfilter element 18. The element 18 is a selectively porous body havingporous region 18a and impervious regions 18b and 180.

The filter 10 beneficially is formed by providing a housing such as thehousing 11 which may be of metal, synthetic resin or a composite ofsynthetic resin and a reinforcing material such as filamentary glass.Beneficially a portion of a flexible open celled foam such as flexiblepolyurethane foam is impregnated with a settable resin such as an epoxyresin. The excess resin is squeezed or otherwise removed from theflexible foam body so that only a thin coating of the hardenable resinremains on the surface of the open cells. The flexible foam body is theninserted Within the passageway 14 and positioned within the enlargedportion of the passage 14a. Advantageously the impregnated foam has adimension slightly greater than the enlarged portion 14a of the passage14 and portions 182; and 180 are collapsed to a suflicient degree toprovide an adhering and sealing quantity of the hardenable resinadjacent the inner surface of the body 11. Subsequent curing of theresin is accomplished by the addition of a hardening agent such as borontrifluoride for an epoxy resin, if the hardening agent is not presentoriginally in the resin with which the open celled flexible foam wasimpregnated. Heat or time provides hardening of the resin therebyproviding a rigid porous structure firmly disposed and adhered withinthe housing 11 and providing a selectively porous body in accordancewith the invention. Beneficially by selecting a flexible foam of adesired cell size almost any desired degree of porosity is obtained. Theporosity can be varied to some extent by the amount of the hardenableresin which is added to the flexible foam and to some extent by thedegree of compression under which the foam is permitted to set. If theimpregnated foam is cured while in the completely collapsed stagenonporous portions such as the portions 18b and 180 are obtained.

In FIG. 2 there is depicted a selectively porous element generallydesignated by the reference 20. The selectively porous element 20 has agenerally elongate cylindrical configuration and comprises an imperviousbody portion 21 and a pervious or porous body portion 22. The element 21defines an internal longitudinal passageway 23. The pervious portion 22provides communication between the passageway 23 and the space externalto the element 20. Beneficially selectively pervious bodies such as thebody 20 in the form of conduits are advantageously employed for thedistribution of liquids in trickle filters, gasliquid contact apparatus,seepage conduits, ventilating systems, spargers, and the like. A bodysuch as the body 20 is readily formed employing apparatus generally asshown in FIGS. 3 and 4.

In FIG. 3 there is depicted mold 25. Mold 25 comprises a portion of acylinder wherein a sector of the cylindrical wall has been removed toform a longitudinal opening 26. A flexible open celled body 28 isdisposed within the mold 25. The body 28 has been treated with ahardenable resin substantially as set forth in US. Pat. 3,269,887. Anexpandable mandrel 29 is disposed within body 28 which is of a hollowcylindrical configuration. The mandrel 29 is adapted to be expandedmechanically or alternately by fluid pressures such as gas or liquid.Advantageously such a mandrel can comprise an elastomeric tube which onthe application of internal pressures will expand to an extentsufiicient that its outer dimension approximates that of the innerdimension of mold 25.

In FIG. 4 the mandrel 29 is expanded to form the enlarged mandrel 29a.The foamed body 28 is compressed in the region 28a and uncompressed inthe region 28b. Compression of the body 28 in the region 28b causescollapse of the cell walls and contact of adjacent cell walls with eachother and in curing of the resin impregnating the flexible foam body,the region 28 forms a rigid, impermeable region. The uncompressedportion 281; has open cells which provide a passage from the interior ofthe body to the exterior and which on curing or hardening of thesettable resin provide an area or region of desired porosity.

Employing the method of the present invention, it is readily seen thatthe selectively porous bodies are obtained which can be of essentiallyconstant composition and chemical properties.

In FIGS. 5 and 6 there is depicted an alternate method of forming aselectively permeable conduit or body in accordance with the invention.In FIG. 5 there is shown a hollow cylindrical mold generally designatedby the reference numeral 35. The hollow mold 35 has an internal cavity36. Within the cavity 36 is an impregnated open celled flexible foamedbody 37 having a. hollow cylindrical configuration disposed within theimpregnated body 37 is an expandable mandrel 38. The mandrel 38comprises a non-expandable or rigid portion 39 and a flexible deformableportion 40. The deformable portion 40 is adapted to expand and generallyfill the cavity 36 on the application of internal pressure.

In FIG. 6 there is depicted the mold 35 having disposed therein the body37 after compression by the mandrel to form a collapsed portion 37a andan uncollapsed portion 37b. The rigid portion 39 of the mandrel servesto contain the uncompressed portion 37b and prevent collapse of thecells. On curing of the settable resin, the portion 37a is imperviouswhile the portion 37b is pervious and the external configuration of theresultant conduit is generally cylindrical. The cylindricalconfiguration is oftentimes desirable wherein the selectively permeableconduit is to be employed with conventional pipe fittings or tubingconnections.

In FIG. 7 there is depicted a view of a gas distributing conduitgenerally designated by the reference numeral 50. The conduit 5t}comprises an impermeable trough 51. The trough 51 has sides 52 and 53, abottom 54 and an end 55. A selectively permeable body 56 forms a face ofthe conduit opposite the bottom 54. The selectively impermeable bodycomprises an impervious region 57 and pervious or permeable regions 58and 59. The selectively pervious portion 56 is formed by theimpregnation of the flexible open celled foam With a settable resin andcompression of the flexible foam in the region 57 as the settable resinis cured, thereby adhering the cell walls together into a generallysolid impermeable member while leaving the cells open in the regions 58and 59.

Advantageously the method of the present invention permits formingselectively permeable articles of almost any desired shape and form bychoosing a suitable foam and impregnating resin.

As is apparent from the foregoing specification, the present inventionis susceptible of being embodied with various alterations andmodifications which may differ particularly from those that have beendescribed in the preceding specification and description. For thisreason, it is to be fully understood that all of the foregoing isintended to be merely illustrative and is not to be construed orinterpreted as being restrictive or otherwise limiting of the presentinvention, excepting as it is set forth and defined in thehereto-appended claims.

What is claimed is:

1. A rigid selectively permeable porous hollow cylindrical bodyconsisting essentially of (a) an axially extending portion of thelightweight flexible foam wherein the cell cells, the open cellspermitting the flow of gas or liquid therethrough, the walls of thecells being coated with a thin film of a hardened resin and a curingagent therefor, and (b) an impervious portion comprising a collapsedportion of the lightweight flexible foam wherein the cell walls areadhered together by the hardened resin.

2. The body of claim 1 having a generally cylindrical configuration anddisposed within a passageway defined by a housing, the passageway havinga first end and a second end, the porous foam portion providingcommunication between the first end and the second end.

3. The body of claim 1 having a generally planar configuration and aplurality of uncollapsed porous regions.

4. The body of claim 1 wherein the flexible foam is a polyurethane foam.

5. The body of claim 1 wherein the resin coating is an epoxy resin.

6 6. A rigid selectively permeable porous hollow cylindri- ReferencesCited cal body consisting essentially of (a) an axially extending UNITEDA S P ATEN S porous portion of a lightweight flexible polyurethane foam2,942,645 6/1960 Edwards having open cells, the open cells permittingthe flow of 3,070,476 12/1962 Miller 161--160 gas or liquidtherethrough, the Walls of the cells being 5 3,256,013 6/1966Baggenstoss coated with a thin film of a hardened epoxy resin and3,269,887 8/1966 Wmdecker 161 160 a curing agent therefor, and (b) animpervious portion MORRIS SUSSMAN, Primary Examiner comprising acollapsed portion of the polyurethane foam wherein the cell Walls areadhered together by the hard- 10 ened epoxy resin. 161119, 160, 184;210457 P0405) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No- 3.572.390 Dated 23 March 1971 Inventor(5) Wallace T.McMichael It is certified that error appears in the above-ideritifie'dpatent and that said Letters Patent are hereby corrected as shown below:

In Column 4, line 56, insert the word porous between extending andportion'; in line 57 delete "wherein the Cell" and insert having openSigned and sealed this 9th day of November 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer ActingCommissioner of Pat

